Apple MacBook Air A1466 notebook triggers power failure repair

Machine model: apple MacBook Air A1466

Motherboard model: 820-00165

Fault symptom: the notebook triggers power failure.

Maintenance process:

A MacBook Air A1466 notebook, when it failed, it was powered off instantly, and the current was about 0.2. When the motherboard was removed, it was found to be a second repair machine, and there were traces of residual welding oil and maintenance on the motherboard.

Apple MacBook Air A1466 notebook triggered power failure maintenance figure 1

Apple MacBook Air A1466 notebook triggered power failure maintenance figure 2

Apple MacBook Air A1466 notebook triggered power failure maintenance figure 3

The bare board of the motherboard is powered off instantly, and the possibility of power failure caused by peripherals is ruled out. The maintenance directions are as follows:

1. BIOS failure, 2. Short circuit on the motherboard, 3. Timing problem, 4. Lack of power supply, 5. Temperature control signal, 6. No load, etc. The BIOS chip has been repaired at home. Oscilloscope measures several major power supplies, such as CPU 1.7V, memory 1.3V, bridge 1.05V, and PP1V8_S3 and PP5V_S4, etc., which all maintain for about 500 milliseconds at the moment of power-on, and then fall down at the same time.

After power failure, the current can be triggered again when it returns to standby 0.02, and the standby PP3V3_S5 is also very stable and has not been turned off, indicating that there is no problem with the voltage after standby and secondary conversion.

Next, let’s see whether the main power supply problem caused the power failure or PG caused the power failure after the power supply was normal. If U1950 is removed, the bridge will not receive PCH_PWROK, the secondary signal will not come out, and the previous signal will not be affected. Let’s see if there is any problem in the section from power supply to PG. After being removed, the current is fixed at 0.18, and there are 3.3V at pins 1, 2 and 8 of U1950, which proves that it is normal from standby to power supply to PG, and the power failure is not caused by these places.

Install U1950, test whether the platform reset PLT_RESET_L sends out and test whether the resistance value reset to each chip after U2071 conversion is short-circuited. There is no movement when the oscilloscope platform is reset, and there is no short circuit on pin 4 of U2071 chip, that is, the bridge does not send PLTRST.

According to the time sequence, the bridge will send out PLTRST after receiving APWROK, but up to now, both pin 5 and pin 3 of U1950R have measured 3.3V of about 500MS, but the bridge has not sent out PLTRST, and there are two cases that the bridge is broken or the conditions are insufficient.

It can also be considered that the standby condition of the bridge is normal if the switch can be triggered again after power failure. The only thing left is whether all kinds of power supplies required by each module of the bridge are normal when it is turned on. Lack of power supply may lead to power failure or code failure. After investigation, there is no action when a power supply is found in the clock module.

It was found that this power supply was renamed from PP1V05_S0 by a 0 ohm resistor R1270. The appearance of this resistor has been damaged, and the 1.05V of the measuring front end has come out. Replace the resistor, and it can run normally when it is powered on, so it will not lose power.

After connecting the screen, I found that SN is not available.

Read out the BIOS, add the serial number, brush it back, and then turn it on. SSN has been displayed normally.

This fault is that the bridge module lacks power supply, which leads to power-on and power-off caused by platform reset. After replacing the resistor, it is normal, and the maintenance is over.